2,2'-oxodisuccinate builder salts, e.g., tetrasodium 2,2'-oxodisuccinate, are attractive and efficient nonphosphorus detergency builders which despite being known since the 1960's have apparently eluded large-scale commercialization.
2,2'-oxodisuccinates are believed to have been first disclosed in U.S. Pat. No. 3,128,287, Berg, issued Apr. 7, 1964. Detergent compositions comprising 2,2'-oxodisuccinate as builder are disclosed in U.S. Pat. No. 3,635,830, Lamberti et al, issued Jan. 18, 1972. 2,2'-oxodisuccinic acid and the tetrasodium salt are freely water-soluble and are understood to act as a builder at least in part by complexing in aqueous solution with the calcium and/or magnesium ions which constitute a major fraction of ions found in wash-water, these latter ions being termed "water hardness".
Another well-known class of laundry detergent ingredients are the zeolites. Zeolite A, especially the sodium-exchanged form (Na-A) is an established laundry detergent builder. See U.S. Pat. No. 4,605,509, Corkill et al, issued Aug. 12, 1986. Zeolite A is substantially insoluble in water, at least by comparison with 2,2'-oxodisuccinate, and is understood to act as a builder, at least in part by trapping water hardness, especially calcium ions, in the unusual "cages" of its molecular structure.
Zeolite A is readily available in industry and is especially useful for detergency building purposes when it is in the 1-10 micron size range.
Recently, it has also become possible to synthesize 2,2'-oxodisuccinate using the attractive method of U.S. Pat. No. 4,798,907, MacBrair, Jr., et al, issued Jan.17, 1989.
The terms "2,2'-oxodisuccinate" and "oxydisuccinate" (apparently synonymous for literature search purposes) also appear with frequency in the literature, especially in recitals of builders for laundry detergent formulae. Exhaustive recital of these references (in excess of one hundred) is not possible here. See, for example U.S. Pat. No. 4,689,167, Collins et al, issued Aug. 25, 1987; U.S. Pat. No. 4,131,558, Bailey et al, issued Dec. 26, 1978; U.S. Pat. No. 4,116,852, Bailey et al, issued Sept. 26, 1978; U.S. Pat. No. 4,089,795, Bailey et al, issued May 16, 1978; U.S. Pat. No. 4,019,998, Benson et al, issued Apr. 26, 1977 and U.S. Pat. No. 3,939,100, Hau et al, issued Feb. 17, 1976. Likewise, there is a great number of disclosures of the use of Zeolite A in laundry detergent compositions.
In light of the extensive literature, it is remarkable that 2,2'-oxodisuccinate is still not actively being used in commerce, especially as a detergency builder.
A significant problem not previously believed to have been reported in the 2,2'-oxodisuccinate literature is that when 2,2'-oxodisuccinate builders are conventionally spray-dried to make a granular laundry detergent with other detergent ingredients such as zeolite builders, detergent surfactants and the like, they produce hygroscopic detergent granules which tend to "cake" or become sticky on storage, especially at high humidity. The severe hygroscopicity of tetrasodium 2,2'-oxodisuccinate can be graphically illustrated simply by overnight exposure of freeze-dried solid tetrasodium 2,2'-oxodisuccinate to a humid atmosphere, when a paste or even a liquid is formed owing to the high water absorption from the atmosphere.
The present invention is therefore directed at providing the granular laundry detergent formulator with a practical and useful solution to the 2,2'-oxodisuccinate hygroscopicity problem.
More specifically, it is an object herein to provide a process for making a built granular laundry detergent wherein at least a portion of the builder component is 2,2'-oxodisuccinate, especially in agglomerated form.
It is a further object to provide novel 2,2'-oxodisuccinate-containing agglomerates generally to the detergent formulator.
A third object is the provision of granular laundry detergent compositions formulated with the agglomerates of the invention.
Other objects, such as the provision of useful fully-formulated granular detergent products, are also secured, as will be seen from the following disclosure.
All percentages and proportions herein are by weight unless otherwise indicated.